The present invention relates to a steering lock for use in vehicles.
A conventional manual steering lock is described in Japanese Patent No. 3183588. In this conventional manual steering lock, a mechanical key, which is inserted in a key cylinder, is turned to engage a lock bar with a steering shaft.
Conventional electric steering locks are described in Japanese Laid-Open Patent Publication Nos. 2002-234419, 2003-063354, 10-138872, and 2002-283964. These conventional electric steering locks include an actuator such as a motor that is powered when a mechanical key, which is inserted in a key cylinder, is turned. A steering shaft is locked by a lock bar driven by the actuator.
FIG. 1 shows a conventional electric steering lock 101. A steering wheel 106 is mounted on a steering shaft 2. The electric steering lock 101 includes a sleeve 3 covering the steering shaft 2, bearings 103 and 104 which rotatably support the steering shaft 2 relative to the sleeve 3, and a housing 10a. The sleeve 3 is supported by part of a vehicle (not shown). The steering shaft 2 includes a gear-shaped rotation restrictor 109. An insertion hole 108 extends through the sleeve 3 at a position corresponding to the rotation restrictor 109.
As shown in FIG. 2, the housing 10a has an arcuate mounting surface 11a, which extends along the surface of the sleeve 3. A lock bar passage 11b opens in the mounting surface 11a. The lock bar passage 11b is connected with the insertion hole 108 of the sleeve 3. The sleeve 3 is held between the housing 10a and a bracket 4. Bolts 5 fasten the housing 10a and the bracket 4 to fix the housing 10a to the sleeve 3.
As shown in FIGS. 1 and 2, a lock bar 61 is housed in the housing 10a. The lock bar 61 has a distal end that extends through the lock bar passage 11b of the housing 10a and the insertion hole 108 and into the sleeve 3. The lock bar 61 moves between a lock position, the state of which is shown by the solid lines in FIG. 2, and an unlock position, the state of which is shown by the broken lines. When in the lock position, the distal end of the lock bar 61 engages with the rotation restrictor 109 and prohibits rotation of the rotation restrictor 109, or rotation of the steering wheel 106. When in the unlock position, the distal end of the lock bar 61 is separated from the rotation restrictor 109 to permit rotation of the rotation restrictor 109, or rotation of the steering wheel 106.
As shown in FIGS. 2 and 3, a lock mechanism, which includes a motor 31 and a transmission mechanism 41a, drives the lock bar 61 and is housed in the housing 10a. The motor 31 is controlled by a steering lock ECU (not shown) housed in the housing 10a. The transmission mechanism 41a transmits the drive force of the motor 31 to the lock bar 61.
The motor 31 is fixed to the inner surface of the housing 10a by a motor bracket 31b. The transmission mechanism 41a includes a worm gear 42a, a helical gear 43a, a rotary shaft 44a, a lock bar support 54a, and a spring 47. The worm gear 42a is fixed to the output shaft of the motor 31. The helical gear 43a meshes with the worm gear 42a. The rotary shaft 44a is fixed to the helical gear 43a. The rotary shaft 44a has a male thread 51a. The male thread 51a engages a female thread 53a extending through the lock bar support 54a, which is L-shaped (see FIG. 3). The lock bar support 54a has a distal end elastically connected to the lock bar 61 by the spring 47. The motor 31 drives and moves the lock bar support 54a along the rotary shaft 44a. The lock bar 61 moves with the lock bar support 54a. 
As shown in FIG. 2, the housing 10a has an opening 15a located opposite to the mounting surface 11a. The transmission mechanism 41a and the motor 31 are arranged in the housing 10a through the opening 15a. A cover 70a closes the opening 15a. A plurality of bolts 128 are fastened to the housing 10a from the outer side of the cover 70a so that the cover 70a is fixed to the end face of the housing 10a. The cover 70a and the heads of the bolts 128 are covered by a protective cover 129, which is fitted to the housing 10a. The protective cover 129 prevents vehicle theft since it makes the cover 70a difficult to remove, and thus the steering lock 101 difficult to dismantle. Accordingly, the protective cover 129 is indispensable for maintaining the theftproof effect of the conventional electric steering lock 101.
However, the protective cover 129 increases the number of components required for the electric steering lock 101. Additionally, the fitting of the protective cover 129 to the housing 10a also decreases the assembly efficiency for the electric steering lock 101.